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DescriptionRichard W.M. Jones
2010-09-24 14:36:01 UTC
Description of problem:
The IB700 and I6300ESB watchdog timers don't include a handler
to reset them when the VM / qemu is reset.
The could lead to a failure case as follows:
(a) guest boots, watchdog is enabled
(b) guest does a reset eg:
echo 'b' > /proc/sysrq-trigger
(note that an ordinary /sbin/reboot wouldn't hit this case
since that would properly disable the watchdog)
(c) the reboot takes longer than the remaining time on the
watchdog
(d) the watchdog therefore fires during the reboot
(e) probably the VM would just reboot again at this point which
is pretty benign, but it could depend on the action that the
user had selected for the watchdog
Version-Release number of selected component (if applicable):
All versions of qemu including upstream.
How reproducible:
Always.
Steps to Reproduce:
For the purpose of this demonstration, I'm going to directly
invoke qemu-kvm. You need a guest with the watchdog daemon
installed and configured. The guest should also have a grub
timeout so you can interrupt the boot.
(1) Run:
qemu-kvm \
-enable-kvm \
-m 1024 -vnc :11 \
-drive file=watchdog-guest.img \
-watchdog i6300esb \
-watchdog-action reset
(2) Wait until this boots, check watchdog daemon is running.
(3) Inside the guest do:
sync
echo 1 > /proc/sys/kernel/sysrq
echo b > /proc/sysrq-trigger
Guest will immediately reboot. Same qemu process will
still be running.
(4) Enter grub as the guest boots (ie. hit Esc), and wait for
a few seconds.
Actual results:
The watchdog will fire, causing the guest to reboot again while
you are waiting in grub.
Expected results:
Watchdog should have been reset by the action of resetting
qemu.
Additional info:
Comment 1Richard W.M. Jones
2010-09-24 16:28:24 UTC
Reproduced on qemu-kvm-0.12.1.2-2.131.el6 as following steps.
Reproduce Procedure:
---------------------
1. boot guest with "-watchdog i6300esb -watchdog-action reset"
2. in the guest, enable watchdog:
#cat /dev/watchdog
3. reboot guest using following commands before watch dog heartbeat expire:
#sync
#echo 1 > /proc/sys/kernel/sysrq
#echo b > /proc/sysrq-trigger
4. enter grub interface, press ESC to interrupt the timer, and wait.
Actual results:
----------------
After step 4, for a few seconds, the guest reset.
Verify this bug on qemu-kvm-0.12.1.2-2.146.el6 as the same steps above.
Actual results:
----------------
After step 4, the guest stay in grub interface without reset.
Conclusion:
-------------
According to above results, this bug has been resolved.
Comment 10Richard W.M. Jones
2011-03-02 10:33:10 UTC
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
http://rhn.redhat.com/errata/RHSA-2011-0534.html
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
http://rhn.redhat.com/errata/RHSA-2011-0534.html
Description of problem: The IB700 and I6300ESB watchdog timers don't include a handler to reset them when the VM / qemu is reset. The could lead to a failure case as follows: (a) guest boots, watchdog is enabled (b) guest does a reset eg: echo 'b' > /proc/sysrq-trigger (note that an ordinary /sbin/reboot wouldn't hit this case since that would properly disable the watchdog) (c) the reboot takes longer than the remaining time on the watchdog (d) the watchdog therefore fires during the reboot (e) probably the VM would just reboot again at this point which is pretty benign, but it could depend on the action that the user had selected for the watchdog Version-Release number of selected component (if applicable): All versions of qemu including upstream. How reproducible: Always. Steps to Reproduce: For the purpose of this demonstration, I'm going to directly invoke qemu-kvm. You need a guest with the watchdog daemon installed and configured. The guest should also have a grub timeout so you can interrupt the boot. (1) Run: qemu-kvm \ -enable-kvm \ -m 1024 -vnc :11 \ -drive file=watchdog-guest.img \ -watchdog i6300esb \ -watchdog-action reset (2) Wait until this boots, check watchdog daemon is running. (3) Inside the guest do: sync echo 1 > /proc/sys/kernel/sysrq echo b > /proc/sysrq-trigger Guest will immediately reboot. Same qemu process will still be running. (4) Enter grub as the guest boots (ie. hit Esc), and wait for a few seconds. Actual results: The watchdog will fire, causing the guest to reboot again while you are waiting in grub. Expected results: Watchdog should have been reset by the action of resetting qemu. Additional info: